Very Revd Stephen Lake ascended to the landmark's nave roof where he blessed and switched on 150 panels, installed thanks to £6 million in funding.
He said: "By embracing this very modern technology, we are celebrating God's gift of creation and making this remarkable building a greener and more sustainable place for future generations.
"We are fortunate to have received overwhelming support for the project and are incredibly grateful to the Heritage Lottery Fund and all the individuals who donated to help make it possible."
The panels were installed by Mypoweruk.com as part of the £6 million Project Pilgrim, which included a £4.6 million grant from the Heritage Lottery Fund.
Ben Harrison, managing partner of Mypower, said: "Everyone has worked together in full cohesion to deliver a common goal, to protect the historic building and create a green energy source for the long-term sustainable future of the Cathedral."
Stephen Boyce, Chair of the Heritage Lottery Fund South West Committee said: "We're delighted to support Project Pilgrim and look forward to celebrating its continuing success."
Gloucester Cathedral, which is nearly 1,000 years old, is thought to be the oldest building of its kind in the world to use solar power in producing its own energy.
The Rt Revd Nicholas Holtam, Bishop of Salisbury, the Church of England's lead bishop for Environmental Affairs and Chair of the Environmental Working Group said: "Sometimes the environmental challenges facing us can seem insurmountable but this outstanding project at Gloucester Cathedral will act as a beacon for others, renewing our hope and energising everyone who cares for our common home.
"They are a great encouragement to the wider Church."